Could anyone tell me what the Guards rank structure is? As I start at catterick on the 7th and I have been told by my recruiter that for example corporal's have an extra cheveron. Would anyone be able to enlighten me on the reason for that. I have checked the internet but all I keep coming up with is the private, Lance corporal, Corporal etc

Glad to see your not leaving your research too late. Might be different from my day, but I think your'll be ok, (if in doubt) by calling the staff: mate,gezzar,man,bro or if you want to be old fashioned mucka. The bloke with the stick will take your food order.
All the best!